Remote control of devices for example remote operation of programs, the volume, the brightness and the colour saturation of television sets, may take place as is known with the aid of infra-red radiation as a means of transmission. With remote control by means of infra-red radiation, pulses of different frequency are radiated by an infra-red emitter, these pulses being received by an infra-red receiver and being converted into electrical commands in dependence on the received frequency or the frequency combination. These electrical commands are used to change programs or to control analog functions.
These transmission paths can obviously be destroyed considerably by disturbing surrounding light, for example, incandescent lamp light, because the infra-red receiver registers the disturbing incandescent light and as a result superimposes a coarse noise of considerable amplitude on the signal received. In order that the instruction emitter present at the receiving end does not respond to the coarse noise, a Schmitt trigger, for example, is connected at the output side of the infra-red receiver, said Schmitt trigger only responding from a certain settable potential threshold onwards and only passing on the pulses freed from the noise to the instruction emitter. In order to achieve this the potential threshold of the trigger must be so set that a signal which has been received and which does not contain any coarse noise makes the trigger respond while a coarse noise caused by disturbing incandescent light still lies below the response threshold.